Talk Morgan Forums Morgan Sports Cars Morgan Three Wheeler & Super 3 Wet Sumping

The specs I've seen for Motul 7100 20w50 is 126.5 cSt @40 deg c.
Morris 20w50 mineral is 153.7 cSt @40 deg c.
So one could assume that at cold engine temps the difference in viscosity could be even greater, basically cold the mineral is thicker than the synthetic.

All great info and makes sense too!

Thanks Luddite ! I gave my proposed 'cause' but forget to add the 'effect' doh

nippymog, being a simple chap, I ever need a fuller explanation than most, and thus prefer to see a fuller picture, my addendum was typed in that frame of mind... (-:

Further to that, when one last journey was completed the engine oil would be hot if not very hot and thus more viscous/thin which seems likely the most likely time for maximum flow in the drain down process, slowing as the oil cools, but even old cold and thicker oil could drain back down into the crankcase in time..?

If I remember correctly the scavenge side of the oil pump was of larger capacity than the pressure side, in order to minimise the amount of oil remaining in the crankcase when the engine was running. I guess that being the case(?) that it could also be reasonably efficient in returning crankcase oil level increase as the result of drain down during lay-up..?

It seems that thin synthetic oil may be required relative to the clearances, material specification and hotter running temperatures of modern engines to assist them to comply with emission regulations (?) and on that point in times past crankcase ventilation was open to atmosphere to avoid pressure build up and reduce oil leakage... IF the modern M3W engine like many others has to swallow it`s crankcase "breather" output that seems likely to be via an air/oil separator feeding back into the inlet tract, and if you take that a stage further, starting an engine with a high oil level in the sump due to a period of lay up, then it seems possible that more pressure seems likely to be created by the crank in what is now somewhat restricted air space...? More pressure seems likely to create more stress on oil sealing of the crankcase and perhaps more pressure on the air/oil separator mechanisms operation, which then may have an impact on mass air flow sensing if higher levels of oil mist is present on start up and subsequent running till the normal operational crankcase oil level is restored...?

Further to all that... it seems many modern car engines suffer intake manifold fouling from the time that direct fuel injection (DFI) was taken on board. Apparently even some performance engines can start suffering a drop off in efficiency in as little as circa 30K miles due to this aspect of emission reduction. Additionally the air oil separator (AOS) is a prime suspect when things really foul up. I have heard where the inlet manifolds have to be stripped off and cleaned out, and where the inlet tract valves in place are blasted with a natural media to clean off the gunge that builds up...

If you have a carb and likely minimal separation of air and oil fed to the air filter, then whatever oil enters the inlet tract has the benefit of fuel to wash it into the combustion chamber and burn it away .

Amazing the knock on or domino effect of a little too much oil in a crankcase.... or have I got that all wrong...? More than happy to be further/better educated...

V300 le mans Motul 20/60 the best

I have used mineral oil on all my air cooled twins over the past 30 years, the MTW is no different. So far I’ve never had an oil related issue but of course I have now set myself up!

Luddite,

Would agree with pretty much everything you've written here. I would point out, though, that the M3W is not direct injection, nor does it have an AOS, just an unfiltered calibrated opening into the inlet manifold.

My conjecture is that wet sumping is not endemic to the X-wedge design, but instead related to inadequate manufacturing quality control of the oil pump. Changing oil to a non recommended, non synthetic should only be viewed as a short term fix. Better to address the underlying issue and replace the oil pump, which is admittedly expensive.

As an additional data point, my machine has about 10k miles, runs 20-50 synthetic (H-D spec) and I started it a few days ago for the first time since early November-so a pretty long lay up. It also has an added AOS setup with a clear reservoir which allows me to see what's being pumped out of the camchest on it's way to the intake. The AOS captured only a tiny amount of frothy oil during the 5 minute warm up period. That of course does not mean I have zero wet sumping going on, only that it is low enough that neat oil isn't being sucked out of the camchest area.

If we were to take a comprehensive survey of how many machines have wet sumping issues vs how many do not, I think that would be useful. We should also remember the rule of forums: negative posts on vehicle problems dominate, as the owners without issues are out enjoying their machines vs searching forums for answers.

“ Changing oil to a non recommended, non synthetic should only be viewed as a short term fix”

The Morgan handbook only recommends synthetic oil for “unusually hot conditions”.

I regret that I've only just seen this thread but want to agree with all of Luddite's first post. I've never run a JAP but have had two or three Matchless's and an Anzani and followed the same starting procedure as Luddite describes; the only difference being that it was the wrist, not the ankle, that suffered if the advance/retard was incorrectly adjusted (assuming one's thumb was not wrapped round the handle!). It was always my practice to turn off isolating cocks on both fuel and oil supply lines if the engine was not going to be run in the next couple of hours or so. As age advanced and memory became less reliable (and use of car less frequent) I hung a reminder card on the ignition switch. I thought when I swapped the Matchless for an S&S I would be spared the 'aggro of antiques'!
Has anyone made any attempt to contact owners of S & S engines in motor cycles or other applications? We could possibly learn from them regarding wet sumping among other topics.
Johnny.

The S&S recommendation is to use (Mobil 1) V-Twin 20w-50 Synthetic oil above 35F ambient temperature. I would tend to go with what S&S recommend for their engine. I have heard some others, who should know what they are talking about, suggest different oils but without any documented back up....... I still think the problem relates to oil pump tolerances but happy to be proven wrong.